Importance

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Abstract

A system for measuring the flow rate of gas includes a flow head having a sensor thermoresistor mounted transversely to the flow of gas, and a reference thermoresistor mounted parallel to the flow of gas, both thermoresistors having equal resistance versus temperature functions. Each thermoresistor is connected in a feedback control circuit, in which each thermoresistor is separately supplied with current to heat it, the current first passing through a fixed resistance in series with each of the thermoresistors. The current supplies are servo controlled to equalize the resistance of each thermoresistor with that of its associated fixed resistance. The power consumed by each thermoresistor at its equilibrium resistance is measured to provide a power indicative signal associated with each thermoresistor. The two power indicative signals are compared to generate a delta power signal. An empirically-derived flow rate-versus-delta power curve is stored as a look-up table in a computer memory. The value of the delta power signal is applied to address the look-up table to acquire the corresponding flow rate value.

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First Claim